In this type of a permanent-magnet embedded motor, a plurality of permanent magnets are embedded in a rotor so as to be adjacent to each other in the circumferential direction of the rotor. In each pair of the adjacent permanent magnets in the circumferential direction of the rotor, the magnetic poles thereof are different from each other. In the surrounding area of a portion where the magnetic poles of each pair of the adjacent permanent magnets are switched, an abrupt change in magnetic flux density occurs. This causes a torque ripple which leads to vibration and noise.
There have been various methods for reducing such a torque ripple. For example, as described in Patent Document 1, recessed and projecting portions or the like are formed at predetermined positions of magnetic-pole switching portions between permanent magnets on the outer circumferential surface of a rotor.